Doors and hatches used in ships and analogous vessels often utilize quick-acting latching mechanisms that allow the door or hatch to be latched and unlatched by rotating a single handle. In many cases, the handle actuates a series of rack and pinion gears, ratchet gears, or levers, which in turn simultaneously actuate a series of dogs located around the periphery of the door. The dogs engage cam surfaces on the door frame or coaming, and pull the door against the frame to form a watertight seal between the door and the frame when the door is closed and latched. Such latching mechanisms are advantageous because they allow the door or hatch to be secured and sealed very rapidly.
Regardless of the manner in which the door is latched, it is often desirable in marine applications to provide a window or port hole in the door to increase visibility through the door. For example, in vessels designed for towing, it is advantageous to have a window in the door to the pilot cabin so the operator may observe the vessel being towed. However, if the window is too small, the operator may have to open the door to check, for example, the condition or position of the vessel being towed. Opening the door may be dangerous because it exposes the pilot cabin to the elements. Larger windows are therefore preferred.
Ample visibility through the pilot cabin door is especially important when towing in inclement weather, when the need to leave the door shut is especially important. Large windows in the doors of engine compartments, and in hatches, are advantageous for similar reasons. Visibility through marine closures is also important since the closures are often located in confined spaces, and a large window opening permits viewing through the closure to see if people are in the way of the closure when it is opened. This is particularly true with closures used in yachting and passenger for hire vessels where persons on board a vessel may not be familiar with normal craft procedures.
The size of the windows in existing marine doors and hatches has been necessarily limited because their latching mechanisms are typically complex, utilizing a system of bulky gears or levers, or other custom mechanisms, which may extend into and thus obstruct the central portion of the door or hatch where the window would be located. Thus, many prior gear-driven or lever-driven latching mechanisms are incompatible with doors having a large central window.
In addition, gear-activated latching mechanisms may be incompatible with anything but square or rectangular doors, and cannot be made to easily accommodate odd, or irregular shaped doors or hatches.
U.S. Pat. No. 2,271,952 discloses a quick-acting, watertight ship door, which utilizes a system of rotatable dogs actuated by a series of rack and pinion gear elements contained within the interior of the door. This mechanism is complicated and unwieldy. In addition, the gear mechanisms are subject to malfunction when fouled by corrosion or when worn.
Other types of latching mechanisms are not adaptable to be used in harsh marine environments. For example, U.S. Pat. No. 4,844,518 discloses, in one embodiment, a chain-and-sprocket mechanism for actuating a plurality of hinged catch latches for sealing a lid on a container. This kind of a latch system is unsuitable for use in a marine environment because, among other reasons, the latch system is not secure enough to withstand the severe environmental stresses present in marine applications. Further, the chain is tensioned by a spring-loaded tensioning device positioned in the central portion of the container lid. This precludes use of the device in a door or hatch having a central window opening.
Thus, there is a need for a quick-acting latching mechanism for marine doors, hatches and other closures, which is adapted for use in harsh marine environments, which may be used in a door having a large window opening, and which may be used in any shape of door or hatch.